Analysis of vertical force in steering system

For an ideal steering system relay arm (tie rod) should follow the same arc as the suspension follows. Practically it is impossible to achieve due to nonlinearities in the motion of suspension. When the wheel moves in the jounce and rebound, relay linkage will follow an arc which will pull the steering arm to the right and causing a left hand steer when located behind the centre of the wheel.

Roll type steer-

When inboard joint located below the wheel centre and linkage also located at rear of front wheel centre, at jounce a left hand steer will be produced and right hand when it goes into rebound.

Steering system forces and moment

Three types of forces are normally seen in vehicle tire.

Normal force (aligning torque) z-direction

Tractive force (Rolling resistance moment) y direction

Lateral force (Overturning moment) x direction

The reaction in the steering system is due to the moment about steering axis, which must be reduce to control the wheel steer angle.